Also I guess they could put a large battery at the charging station so it can take say a steady 200kw from the grid and be able to kick out 1500kw for ten minutes occasionally. That could also charge from cheap off peak electricity.
BYD's megawatt charging does exactly that.
Tbe best part, the "large battery" uses the same battary on BYD cars. The same electric components, cooling system, etc.
It's simply cheaper to have on-site batteries. It makes installation work with a smaller connection to the grid, and makes it possible to install chargers in more places without upgrading the grid connection.
Energy arbitrage is profitable on its own, so EV charging stations are almost just an excuse to get some land and a grid connection for more batteries.